Moderate Recovery Unnecessary to Sustain High Stroke Volume during Interval Training. A Brief Report

It has been suggested that the time spent at a high stroke volume (SV) is important for improving maximal cardiac function. The aim of this study was to examine the effect of recovery intensity on cardiovascular parameters during a typical high-intensity interval training (HIIT) session in fourteen well-trained cyclists. Oxygen consumption (VO2), heart rate (HR), SV, cardiac output (Qc), and oxygenation of vastus lateralis (TSI) were measured during a HIIT (3×3-min work period, 2 min of recovery) session on two occasions. VO2, HR and Qc were largely higher during moderate-intensity (60%) compared with low-intensity (30%) (VO2, effect size; ES = +2.6; HR, ES = +2.8; Qc, ES = +2.2) and passive (HR, ES = +2.2; Qc, ES = +1.7) recovery. By contrast, there was no clear difference in SV between the three recovery conditions, with the SV during the two active recovery periods not being substantially different than during exercise (60%, ES = -0.1; 30%, ES = -0.2). To conclude, moderate-intensity recovery may not be required to maintain a high SV during HIIT. Key pointsModerate-intensity recovery periods may not be necessary to maintain high stroke volume during the exercise intervals of HIIT.Stroke volume did not surpass the levels attained during the exercise intervals during the recovery periods of HIIT.The practical implication of these finding is that reducing the intensity of the recovery period during a HIIT protocol may prolong the time to exhaustion, potentially allowing completion of additional high-intensity intervals increasing the time accumulated at maximal cardiac output.